EFIDynoTuning Forum

Hi All, posting for some guidance and to talk through my thinking.

Background, Decipha tuned my HCI 302, that had a rocker arm C-Clip drop down into the oil pump and destroy the rotating assembly.

Built a N/A 331, Same heads, Different Intake manifold, More compression, Same custom camshaft from the 302 but installed 4 degrees retarded.
All electronics are the same, Injectors, MAF, Sampling tube etc.

What ive left the same from the original tune (GUFX)
1.K-contstant
2. Injector High and low slopes
3. Injector Breakpoint
4. MAF curve (assumed since same sampling tube, and meter, this could be left the same.

What ive changed so far
1. Crank PW table. More fuel for the large displacement
2. SARCHG to a 331.62ci

Car starts great, idles well, and then part throttle fuel error is generally very good. I do see some funky stuff at idle sometimes, but i am using both HEGO's with longtubes and an X-pipe. Think thats why im seeing some small bank to bank differences as well.

At WOT im seeing some lambse numbers that are very rich, trying to figure out why. HEGO's being pinned rich also confirm that it is rich. I think its all from PERLOAD being off? Itll dip into the .7lambda range at tip in and as you climb in RPM. Data logged and looked at the TP_N_Perload histogram. Looking like my FN035A values all need to drop, but is a VE/Load 87.514 reasonable at peak? Low RPM im seeing numbers that would put me in the 60% range.

Considering the cam is the same, and there is more cylinder to fill, a drop in VE isnt unreasonable correct?

Short pull attached. Itll pull up to 6700rpm, this i shut off short just to get decent data for PERLOAD

You got the right idea but you need to reduce fn035 by the sarchg difference as well. SBF's are head limited engines so anytime you increase displacement your load is going to drop with all else being the same since the head can't flow anymore.

Your tune is corrupted, you have some code changed in the pip routine that shouldn't be.

The lambse is .1 richer than operating temp since the engine is still in startup enrichment.

Here you go, this is your last tune updated with the newest code and adjusted for the 331.

Thanks! Makes total sense on head limitation dropping load. Going to compare the Bins in Tunerpro a bit before i ask any more questions.

Any idea how i corrupted it? I was messing around with the 2 step function awhile back.

yeah was probably the old 2 step code that corrupted it as it does manipulate the pip routine

that would make sense as it may not be corrupted it may just be my old 2 step code from back in the day

if you want to move to your private thread we can do a step 1 and dial it all in